Pennwalt Agru Plastics Ltd. Offers Frost Resistant Medium Density Polyethylene - MDPE Pipes. Pennwalt Agru Plastics Ltd. Is an ISO 9001:2000 registered company. Frost Resistant Medium Density Polyethylene - MDPE Pipes has the features of balance rigidity and toughness. Frost Resistant Medium Density Polyethylene - MDPE Pipes are the preferred means for transportation and distribution of natural gas worldwide. This pipe is provided with high resistance to slow crack propagation, to subsidence, traffic vibration, point loading, and marshy ground.